Bushing insulator



f March 12, 1935. A. AUSTIN BUsHING INsULAToR Filed Spt. 25, 1931 Mill. Lmmg Fig] Figi? lNvENToR Arf/7W OAL/57m BYWW ATTOR' Patented Mar. 12, 1935 PATENT OFFICE BUsmNG INSULA'ron Arthur 0. Austin, near Barberton, Ohio, assignor, lby mesne assignments, to The Ohio Brass Company, Mansfield, Ohio, a corporation of New Jersey Application September 25, 1931, Serial No. 565,047

12 claims.

This invention relates to bushing insulators, and has for one of itsobjects the provision of an insulator of this nature which will contain an insulating fluid without danger of leakage.

A further object of the invention is to provide in a bushing insulator having a pair of dielectric shell or housing members held together by an internal stress member, resilient means to compensate for unequal expansion and contraction of the insulator parts.

A further object of the invention is to provide a bushing insulator having a spring take-up and a conductor for the current which will not cause heating of the spring.

. A further object of the invention is to provide a bushing insulator which is economical to manufacture and of improved construction and operation.

Other objects and advantages will appear from the following description.

The invention is exemplified by the combination and arrangement of parts shown in the accompanying drawing and described in the following specification, and it is more particularly pointed out in the appended claims. i

' In the drawing:

Fig. 1 is a part elevation and part section of one form of bushing insulator embodying the present invention.

Figs. 2 and 3 are fragmentary views similar to Fig. 1 showing modifications.

In bushing insulators, particularly those for high voltage work where it is desired to carry conductor leads through the walls or covers of transformers or oil circuit breakers or where the 'leads arev carried through walls, roofs or partitions, it is frequently difllcult to obtain a good electrical and mechanical construction without increasing the cost or difliculty of manufacture. This is particularly true where moderate or heavy currents must be provided for.

In the form of the invention shown in Fig. 1, insulating elements 10 and 11 form the outside v of a bushing housing or closure. The housing members are clamped to a flange 12 by means of a rod 13 which is provided with a nut or other suitable tightening means 14. The current is carried by a conducting tube 15 which is in electrical contact with the lower terminal 16. The termina putes 1': and 1s are provided with gaskets 19 and 20 which, with the gaskets 21 and 22, make it possible to form an oil or air tight enclosure.

In order to provide for any contraction in the gaskets and for differential expansion or contraction between the metallic members and the dielectric members, it is necessary to provide re1 siliency in the tightening system. Considerable resiliency may be provided by the use of a spring member 23 which transfers the force exerted by the rod 13 to the terminal member 18. In general, it isl preferable to make the tension rod 13 from a strong metal such as steel. Since, how" ever, steel is a poor electrical conductor, it would become hot due to the current iiowing therein, and the current carrying capacity of the busln1 ing would be seriously limited by this member.

In order to provide current carrying capacity, a tubular member is provided which is preferably of copper, aluminum or other good conducting material. It would be diiiicult to maintain direct electrical contact between this member l5 and the upperterminal 18 for any con traction or expansion of Athe member 15 with respect to the outer sleeve or case which would necessitate movement between the two parts. It is difilcult to provide high current conductivity by means of slip joints without a considerable cost.

In the present invention, the tubular member 15 is provided with a ex/ible extension 25 which may be brazed or soldered to the tubular member. The member 25 may be in the form of a tubular braid, wire or exible tubing as desired, providing this member has sufficient current carrying capacity. The upper end of the braid 25 is extended underneath the pressure washer 26. The pressure exerted by the'washer 26 will cause good electrical contact to be maintained between the braid or flexible member 25 and the terminal plate 18 which is preferably provided with upstanding side walls forming a housing 27 for the spring take-up member` 23, and also serving to conduct the currentoutside of the spring member 23. The braid 25 may be soldered or otherwise attached to the terminal plate 18. In general, however, all that is necessary is to insure a positive contact which will be maintained at all times by the spring 23, thus making it easy to assemble or disassemble the bushing. The path of the current will be through the outside of the housing 27 to the terminal24 to which leads may be attached. This arrangement makes it possible.

way desired. Where a chamber at the top of the bushing is not used, the current may be taken directly from the terminal plate 18 or even from an extension of the flexible member 25.

In the construction shown, several advantages are obtained. The use of a tubular conducting member makes it possible to provide space on the inside for the clamping rod 13l and also for a tubular member 29 which terminates in an outlet 30. The space between the rod and the tubular member also provides for circulating oil for cooling purposes. The oil may enter at an opening 31 and discharge through openings in the flexible member 25, thereby causing a cooling of the tube. This makes it possible to provide the tubular member with an insulation Ilayer 32 which may have poor heat conductivity. Since the tube 29 terminates at the lower end of the bushing, oil may be drawn or siphoned from the bottom of the bushing throughthis tube. This is a decided advantage as it takes the oil of lowest dielectric strength from the bushing and makes it possible to service the bushing without detaching terminals or moving the bushing from position. A filling plug 33 may be used to determine the oil height in the bushing when desired. The construction is such, however, that danger oi' leakage is practically eliminated so that provision for inspection of the bushing is of little or no importance after the bushing is once illled.

The arrangement makes it possible to use a conducting and tightening member of ferrous material and an outer conducting sleeve of nonferrous material and, at the same time, insure a hermetically sealed bushing case; provision being made for diiferential expansion and continuous clamping for the various members.

With the arrangement shown, it is not necessary for the current to flow through the portion of the rod 13 inside the spring 23. Where current flows through the center of a spring made of ferrous material, the losses due to eddy current and hysteresis in the metal of the spring may limit the current capacity of the bushing. Where the current is vconductedoutsideoif the spring, as in the arrangement shown, ux in the spring member will be avoided or reduced to a negligible point, ,thereby permitting high current vcarrying capacity.

Fig. 2 shows one form of the invention in which the conducting tube 34 is used for a clamping member as well as for a conducting member. Current carrying conductivity between the member 34 and the terminal plate 18 is provided by flexible jumpers 35. The pressure exerted by the spring 23 insures contact between the jumpers 35 and the conducting parts. The magnetic ux set up in the spring member 23 is readily neutralized by a short circuit turn or short circuit turns 36, preferably of flexible material, so as to permit free movement of the clamping mechanism. The short circuitturn 36 reduces the magnetic flux in the spring 23 so that heating may be reduced to practically any desired value. Ii' the bushing is open to the air, a slight. amount of heat is an advantage as it tends to keep the oil above air temperature. This reduces the tendency to take up water from the air d ue to breathing action of the bushing.

Where a tension rod 13, like that shown in Fig. 1, is used, the tension in this rod will tend to maintain thel position of the conducting tube or member 15. Therefore, this member may be of flexible material such as braid or a hollow cable, as shown at in Fig. 3. Wherea hollow cable is used, there is usually sufllcient flexibility owing to the lay of the cable so that the ends of the cable can be bent over the terminal plate 18, as shown at 38. With this construction a paper or varnished cambric wound cable may be used for the core or central insulating member of the bushing. It is generally preferable, however, to use a porcelain or vitreous sleeve or baille 39 to protect the paper or varnished cambric from charging current. 'I'his sleeve should preferably have a metalized surface of suitable design, as shown at 40 in Fig. 1. This surface is connected directly to the flange 12 or to a capacitance outlet member 41.

I claim:

1. An insulator bushing having a metallic stress member extending therethrough, a coil spring surrounding said stress member and exerting tension thereon, and'means outside of the coil formed by said spring for conducting the current which passes through said bushing, said outside conducting means having much greater conductivity than said stress member so that the major portion of said current passes through said outside conductor and only a minor portion thereof passes through the interior of said coil.

2. An insulator bushing comprising a pair of complementary shell members, a stress member extending through said shell members and holding said shell members together, a coil spring for exerting tension on said stress member, and a main conductor other than said stress member extending through said insulator, said main conductor being disposed outside of the coil formed by said spring.

3. An Ainsulator comprising complementary shell members, a supporting flange extending between adjacent ends of said shell members, a stress member extending through said insulator for clamping said shell members against said flange, a spring surrounding said stress member and exerting force on said shell members for resiliently holding said shell members together, and a main conductor disposed outside of said spring for conducting the current passing through said insulator, said main conductor having a much greater conductivity than said stress member so that the major portion of said current passes through said main conductor and only a minor portion thereof passes through the in.

terior of said coil.

4. A bushing insulator comprising a pair of shell members, a central ilange disposed between adjacent ends of said shell members, a stress member extending through said bushing insulator, holding members secured to said stress member and having bearing connection with the ends of said respective shell'members for holding said shell members against said flange, a helical spring surrounding said stress member at one end of said bushing and bearing upon one of said holding members for exerting force on said stress member and said shell members to hold said shell members resilientlyv against said flange, a conductor extending through said bushing insulator and surrounding said stress member, a terminal for said conductor, and means disposed outside of said spring for connecting said terminal with said conductor. V

5. A bushing insulator comprising a pair of shell members, terminals at opposite ends respectively oi' said insulator, a stress membervextending through said shell member for holding said shell members together, a spring for exerting tension on said stress member, anda coning through said insulator.

6. An insulator comprising a pair of shell members, a stress member extending through said insulator for holding said shell members together, a spring for exerting tension on said stress member, a' conductor extending through said shell members, a terminal for said conductor at one end of said insulator, and a ilexlble jumper connecting said conductor with said terminal.

'1. An insulator comprising a pair of shell members, a stress member extending through said insulator for holding said shell members together, a spring for exerting tension on said stress member, a tubular conductor loosely surrounding said sftress member, and a drain tube extending through the space between said conductor and stress member.

8. An insulator comprising separately formed dielectric parts, a stress member extending through said parts for holding said parts together, a spring exerting tension on said stress member, a conductor tube surrounding said stress member, a terminal for said conductor tube, and a tubular member ot flexible material electrically connecting said conductor tube and said terminal and held in contact with said terminal by said spring.

9. An insulator comprising a pair of dielectric shell members having opposed open ends forming a closed housing, a closure plate for the lower end of said insulator, a closed reservoir forming a tight closure with the upper end oi said insulator, a stress member connected with said closure plate and extending through said insulator into said reservoir, a spring disposed in said reservoir and holding said reservoir in tight connection with the upper end of said insulator, means connecting said spring with said stress member to exert torce on said' stress member and said reservoir and a conductor connected with said reservoir and said closure plate.

10. A bushing insulator comprising a pair of tubular dielectric shell members having opposed bearing shoulders, a supporting ring interposed between said shoulders, .bearing members engaging the ends oi said shell members at opposite ends of said bushing respectively, a conductor member and a metallic stress member disposed one within the other and both extending through said ring within said shell members and insulated from said ring by said shell members, said metallic stress member extending entirely through said shell members and having one end thereof iixed to one of said bearing members, a stop secured to 'the other end of said metallic stress member, and a spring interposed between said stop and the other of said bearing members and cooperating with said stress member and said bearing members for holding said shell members together in assembled relation with said ring, one end oi said conductor member being fixed to one of said bearing members while the other end of said conductor member is longitudinally movable relative to the other of said bearing members, and a flexible conductor connecting the longitudinally movable end of said conductor and s aid last named bearing member.

1l. A bushing insulator comprising a pair of dielectric members, a stress rod extending through said insulator, a spring cooperating with said stress rod and with said dielectric members to hold said insulator in assembled relation, a terminal member for said insulator, and a iiexible conductor held in electrical contact -with said terminal by said spring.

l2. An insulator comprising a pair of tubular dielectric members, a conductor extending through said insulator and having one end thereof movable relative to the adjacent end of said insulator, a terminal i'or said conductor, a flexible jumper connecting the movable end oi said conductor with said terminal, and a spring for holding the dielectric members of said insulators in assembled relation, said ilexible jumper being held in electrical contact with said terminal by said spring.

ARTHUR O. AUSTIN. 

